instanceof

How to I test if a is a subclass of b ? Class<?> a = A.class; Class<?> b = B.class; Are you looking for: Super.class.isAssignableFrom(Sub.class) Rob Hruska If you want to know whether or not a Class extends another, use Class#isAssignableFrom(Class) . For your example, it would be: if(B.class.isAssignableFrom(A.class)) { ... } If you're interested in whether or not an instance is of a particular type, use instanceof : A obj = new A(); if(obj instanceof B) { ... } Note that these will return true if the class/instance is a member of the type hierarchy and are not restrictive to direct

It has been repeatedly said that the instanceof operator should not be used except in the equals() method, otherwise it's a bad OOP design. Some wrote that this is a heavy operation, but it seems that, at least java, handles it pretty well (even more efficiently than Object.toString() comparison). Can someone please explain, or direct me to some article which explains why is it a bad design? Consider this: Class Man{ doThingsWithAnimals(List<Animal> animals){ for(Animal animal : animals){ if(animal instanceOf Fish){ eatIt(animal); } else if(animal instanceof Dog){ playWithIt(animal); } } } ...

hibernate 只需要操作对象就可以对数据库的数据进行“增删改查”。用了短时间后，感觉依旧存在很大的冗余。正因为这个，我的反射框架就出现了。因为自用，下面只贴出代码，不做解释。有兴趣的可以来看看一起研究一下，如有问题可私聊探讨。 反射基类 SQLSuper /** * 给对象做反射并且定于返回HQL语句方法的抽象类 * @author vincent Mao * */ public abstract class SQLSuper { /** * */ protected StringBuffer SQL; public StringBuffer getSQL() { return SQL; } public void setSQL(StringBuffer sQL) { SQL = sQL; } /** * 根据传入的实体对象and条件集合and排序对象返回HQL语句 * @param obj 经过重新封装的实体类 * @param condition 条件集合 * @param orderBy 排序对象 * @return HQL */ public abstract String getSQL(Object obj , List condition,OrderBy orderBy); /** * 返回所有类的名字 * @param tables * @return List

一、protobuf环境搭建 Github 地址: https://github.com/protocolbuffers/protobuf 然后进入下载页 https://github.com/protocolbuffers/protobuf/releases 下载系统对应版本编译器 我这里使用的是window 64位 下好之后解压，然后把bin里面的protoc.exe加入到环境变量， 并且把protoc.exe拷贝到C:\Windows\System32 二、创建Student.proto 文件 syntax = "proto2"; package com.example.protobuf; option optimize_for = SPEED; option java_package = "com.example.protobuf"; option java_outer_classname = "DataInfo"; message Student{ required string name = 1; optional int32 age = 2; optional string address = 3; } 　　 在工程中增加依赖 <dependency> <groupId>com.google.protobuf</groupId> <artifactId

来源： https://www.cnblogs.com/jie-xuan/p/11330959.html